A planetary gear device including a planetary gear, in which a gear center shaft engages with a cylindrical internal gear and revolves, and a sun gear at the center of the planetary gear engaging with the planetary gear, is small in size and lightweight and is a gear device that can increase a reduction gear ratio. The planetary gear devices are used for various applications such as speed reduction devices, transmissions and pumps.
In the planetary gear device, lubrication is essential for bearings supporting the planetary gears and rotating members, and teeth surfaces of engaging gears. The bearings and engaging gear surfaces of the planetary gear device are generally lubricated with lubricating oil. A gap exists between opposing surfaces of a fixed portion supporting the gear device and an input rotation portion input and/or an output rotation portion input from/output to the outside due to the relative movement of the opposing surfaces, and a lubricating oil sealed inside the gear device may leak to the outside of the gear device. Therefore, various types of seal members are used in the gap of a rotation portion to prevent oil leakage.
For example, Patent Literature 1 describes an oil lubrication structure of an automatic transmission using a planetary gear device. In the oil lubrication structure of Patent Literature 1, as described in paragraph 0037 and FIG. 1, a seal member is disposed on the rim of a clutch piston of a clutch device. Patent Literature 2 describes a bearing lubrication device for a gear box. In the bearing lubrication device of Patent Literature 2, as described in paragraph 0049 and FIG. 1F, a lip seal disposed between a retainer and a stationary pipe holds a lubrication agent such as lubricating oil for bearings and other components.